The 2013 Billboard Music Awards rolled into Las Vegas on Sunday night taking over the MGM Grand. Stars hit the Billboard red carpet and made appearances on stage, but the real fun went on behind the scenes and in the audience. Check out celebrities and performers mingling backstage and posing for photo ops in between winning awards and grabbing the microphone. Jennifer Lopez shared a kiss with boyfriend Casper Smart, while Selena Gomez flaunted her gold costume, plus Miley Cyrus, Ke$ha, Madonna, and more mingled backstage. Make sure to check out all the highlights from the Billboard Awards!